1. Field of the invention
The present invention relates to a vibrating gyroscope, and particularly to a vibrating gyroscope using bending vibration of pillar shaped vibrator.
2. Description of the Prior Art
FIG. 15 is an illustrating view showing a conventional vibrating gyroscope. The vibrating gyroscope 1 has a vibrating body 2 of regular triangular prism shape. Piezoelectric elements 3a, 3b and 3c are formed on three side faces of the vibrating body 2. The piezoelectric elements 3a and 3b are used for driving a bending vibration on the vibrating body 2, and are also used for detecting output signal corresponding to a rotational angular velocity. The piezoelectric element 3c is used for a feedback when driving the vibrator 2. An oscillation circuit 4 is connected between the piezoelectric elements 3a, 3b and the piezoelectric element 3c. The piezoelectric elements 3a and 3b are connected to input terminals of a differential circuit 5. An output terminal of the differential circuit 5 is connected to a synchronous detecting circuit 6. The synchronous detecting circuit 6 is connected to a smoothing circuit 7.
In this vibrating gyroscope 1, the vibrating body 2 vibrates in bending mode in the direction perpendicular to the face that the piezoelectric element 3c is formed, in accordance with a driving signal generated by the oscillation circuit 4. When the vibrating gyroscope 1 rotates around an axis of the vibrating body 2, a vibrating motion of the vibrating body 2 changes a direction by Coriolis force. It causes a difference of output signals between the piezoelectric elements 3a and 3b, and the difference is obtained from the differential circuit 5. A signal corresponding to the rotational angular velocity applied to the vibrating gyroscope 1 is obtained by detecting an output signal from the differential circuit 5 and smoothing a measured signal.
As shown in FIG. 16, the oscillation circuit 4 includes, for example, an amplifier 8 and a phase shifter 9 connected with each other. As the phase shifter 9, a CR filter having a resistor and a capacitor is used.
In the vibrating gyroscope 1, the signal from the piezoelectric element 3c for feedback is amplified by the amplifier 8, and a phase of the signal is modulated by the phase shifter 9. The vibrating body 2 is self-oscillated by applying an output signal from the phase shifter 9 to the piezoelectric elements 3a and 3b for driving.
In the vibrating gyroscope 1 shown in FIG. 15, however, a detecting sensitivity is affected by a variation of the environment temperature. A temperature characteristic of the detecting sensitivity depends on a combination with temperature characteristics of the vibrator, the oscillation circuit and the detecting circuit. It has been a difficult problem to compensate the sensitivity changed by the temperature variation.
Owing to the temperature characteristic of the oscillation circuit, a driving signal voltage required for exciting bending vibration to the vibrating body is fluctuated by the variation of the environment temperature. A vibration mode of the vibrating body changes by the variation of the environment temperature. Then, the detecting sensitivity of the rotational angular velocity changes in the vibrating gyroscope.